An expert system for treatment of both analog and binary information from a disturbance recorder is described in a report by K. Salo: "Expert System for the Analysis of Disturbances", presented at the Symposium on Expert System Applications to Power Systems, Stockholm-Helsinki 1988. However, the report does not deal with how the analog information is to be preliminarily treated before it is supplied as input data to the expert system.
In a report by B. Hakavik, et al: "Knowledgebased Registration of Disturbance Data", also presented at the above-mentioned symposium, an expert system for analysis of binary information or alarm is described. The main purpose of the applications described in the report, however, is to reduce the number of alarms to which a human operator is exposed. The analysis is performed by grouping the alarms, by means of logical conditions, into a number of different primary events.
Analog signals have been treated by expert systems for analysis of vibrations. This has been a relatively successful application when it comes to studying, for example, vibrations from a steam turbine. However, these systems are based on frequency domain analysis of the analog signals, whereby the time related aspects are to a certain extent lost.
Systems for automatic analysis of ECG (electrocardiogram) signals have also been described in the literature. This is basically analysis of analog signals with the aid of expert systems; see, inter alia, "A Contribution to the Automatic Processing of Electrocardiograms Using Syntactic Methods", by G. Belforte, et al, published in IEEE Trans. on Biomedical Eng., Vol. BME-26, No. 3, March 1979, pp. 125-136, and EP application EP 0 292 351 A1, "Systeme de traitement de signal". The methods described are based on techniques using pattern recognition, whereby a classification into an finite number of patterns takes place. The method is primarily applied where it is desired to identify a number of previously known signal patterns.
There is a need for expert systems for analysis of both analog and binary signals from electric power systems. In such a system it is highly desirable to be able to describe both analog and binary signals in a similar manner. The representation of the analog signals which is aimed at is a representation similar to that used for binary signals, that is, either true or false within a certain time interval. The prior art described above for analysis using expert systems, however, proposes no such representation of analog signals.